Transistors have many applications. For example, transistors can be used as a switch or can be used to amplify an input current. As a switch, a transistor may be either fully “on” with maximum current flow, or fully “off” with minimal, ideally zero, current. As an amplifier, a transistor can amplify the small output current from a logic chip so that it can operate a larger device such as a relay or other high current device. Transistors are incorporated into most electrical circuits.
Designers strive to make continuous improvements to make transistors smaller and exhibit improved performance.